CN106856297B

CN106856297B - Spark plug

Info

Publication number: CN106856297B
Application number: CN201610882091.5A
Authority: CN
Inventors: 李政勋; 李东洙
Original assignee: Hyundai Motor Co
Current assignee: Hyundai Motor Co
Priority date: 2015-12-09
Filing date: 2016-10-09
Publication date: 2020-05-19
Anticipated expiration: 2036-10-09
Also published as: CN106856297A; US20170170635A1; KR101786238B1; US9853422B2; KR20170068713A

Abstract

A spark plug may include: a center electrode disposed in a center portion of the spark plug; an insulator surrounding the center electrode; and a metal shell surrounding the insulator and having a ground electrode extending downward from a lower end of the metal shell and an inner surface facing the insulator, the inner surface being concavely shaped to form a shield space for adjusting a heat range of the spark plug between a concave portion of the inner surface and the insulator.

Description

Spark plug

Technical Field

The present invention relates to a spark plug, and more particularly, to a spark plug installed in a combustion chamber of an engine for a vehicle to ignite a fuel-air mixture by generating a spark.

Background

Generally, a spark plug used in a gasoline engine for a vehicle includes: a center electrode disposed in a center portion of the spark plug; an insulator surrounding the center electrode; a metal shell surrounding the insulator; and a ground electrode extending downward from a lower end of the metal shell. A spark current is generated between the center electrode and the ground electrode, and the spark occurring at this time ignites the fuel-air mixture compressed in the combustion chamber.

As shown in fig. 6, the spark plug is classified into a hot type, a medium type, and a cold type according to the length of a length portion (portion C) exposed to the combustion chamber. Reference numeral 602 denotes an insulator, reference numeral 603 denotes a metal shell, reference numeral 604 denotes a hexagonal nut, reference numeral 605 denotes an insulator tip, and reference numeral 610 denotes a ground electrode. The classification is determined based on a heat range indicating a degree of heat dissipation of the spark plug. The hot type spark plug has a low heat dissipation effect, and the cold type spark plug has a high heat dissipation effect. As is known from fig. 6, because the length portion of the cold type spark plug is relatively short, the heat absorbing area of the cold type spark plug is reduced and the heat dissipating area is increased, and thus the heat source available to the spark plug during combustion is small. In contrast, since the length portion of the thermal type spark plug is relatively long, the heat absorbing area of the thermal type spark plug is increased and the heat dissipating area is reduced, and thus the heat source available to the spark plug during combustion is large.

In order to optimize combustion in the engine, a spark plug having a heat range suitable for the engine characteristics is used. However, in the case of a turbocharged gasoline direct injection (T-GDI) engine equipped with a turbocharger, it is difficult to employ a spark plug having a heat range suitable for engine characteristics.

Generally, the temperature and pressure of combustion in a T-GDI engine are greatly increased as compared to a Naturally Aspirated (NA) engine due to over-supercharging of the turbocharger. Such a combustion environment may increase the likelihood of pre-ignition and knock phenomena due to pre-ignition, which may abnormally increase the temperature and pressure in the combustion chamber. The high combustion pressures and pressure waves in the combustion chamber due to repeated knock can burn the spark plug's insulator and can lead to incomplete combustion and engine overheating.

For this reason, although the cold type spark plug is not entirely appropriate, it is applied to a T-GDI engine in order to cope with high combustion pressure and pressure wave at the time of occurrence of knocking. This is because the cold type spark plug having a relatively short length portion can increase the overall strength of the insulator. However, since the cold type spark plug keeps the heat quantity poor and dissipates the heat fast, the temperature of the spark plug cannot quickly reach the self-cleaning temperature when the engine is initially started, which may cause problems of engine ignition failure and deterioration of the cold start operation efficiency.

The information disclosed in this background section of the invention is only for enhancement of understanding of the general background of the invention and is not to be taken as an acknowledgement or any form of suggestion that this information constitutes prior art that is known to a person skilled in the art.

Disclosure of Invention

Various aspects of the present invention are directed to provide a spark plug that prevents an insulator and its own plug from being burned out by high combustion pressure and pressure waves, improves cold start operation of an engine, and prevents misfire.

According to various aspects of the present invention, a spark plug may include: a center electrode disposed in a center portion of the spark plug; an insulator surrounding the center electrode; and a metal shell surrounding the insulator and having a ground electrode extending downward from a lower end of the metal shell and an inner surface facing the insulator, the inner surface being concavely shaped to form a shield space for adjusting a heat range of the spark plug between a concave portion of the inner surface and the insulator.

The shielding space may be located in an intermediate position between the hexagonal nut and the insulator tip.

The inner surface of the metal case may be concavely shaped to form a shielding space, and the shielding space may have a quadrangular cross section.

The shielded space may have a rectangular cross-section defined by a height and a bottom thereof, the height being greater in size than the bottom.

The inner surface of the metal case may be concavely shaped to form a shielding space, and the shielding space may have an uneven section including concave portions and convex portions, which are alternately arranged on the inner surface of the metal case at predetermined intervals in the axial direction.

The inner surface of the metal case may be concavely shaped to form a shielding space, and the shielding space may have a saw-toothed cross-section including threaded portions (threaded portions) arranged on the inner surface at predetermined intervals in the axial direction.

The inner surface of the metal shell may be concavely shaped to form a shielded space, and an insulating material may be disposed in the shielded space.

The overall shape of the shielded space may be a hollow cylinder.

It should be understood that the term "vehicle" or "vehicular" or other similar terms as used herein include a broad range of motor vehicles, such as passenger vehicles including Sport Utility Vehicles (SUVs), buses, trucks, various commercial vehicles; watercraft including various boats and ships; aircraft and the like; and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuel derived from non-petroleum sources). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, for example, gasoline-powered and electric-powered vehicles.

The method and apparatus of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and which together with the following detailed description serve to explain certain principles of the invention.

Drawings

Fig. 1 is a view showing an exemplary spark plug according to the present invention.

Fig. 2, 3, 4, and 5 are views illustrating an exemplary spark plug according to the present invention.

Fig. 6 is a view illustrating a typical spark plug classified based on a heat range according to the related art.

FIG. 7 is a graph illustrating the temperature of heat applied to an exemplary spark plug as a function of vehicle speed.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and use environment.

Detailed Description

Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with the exemplary embodiments, it will be understood that the description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

Fig. 1 is a view showing a spark plug according to various embodiments of the present invention, and fig. 2 to 5 are views respectively showing a spark plug according to various embodiments of the present invention. Fig. 6 is a view showing a typical spark plug classified based on a heat range, and fig. 7 is a graph showing a temperature of heat applied to the spark plug depending on a vehicle speed.

The spark plug according to various embodiments of the present invention includes: a center electrode 100 disposed in a center portion of the spark plug; an insulator 200 surrounding the center electrode 100; and a metal shell 300 surrounding the insulator 200 and having a ground electrode 310 extending downward from a lower end thereof and an inner surface 330 facing the insulator 200, a portion of the inner surface 330 of the metal shell 300 being concavely shaped to form a shielding space 350 between the concave portion of the inner surface 330 and the insulator 200 to adjust a heat range.

In this specification, a spark plug applied to a T-GDI engine equipped with a turbocharger is shown, and will now be described as an example. As shown in fig. 6, the spark plug is generally classified into a hot type and a cold type according to the length of a length portion (portion C) exposed to the combustion chamber. Although the cold type spark plug is not completely suitable (up to 750 c to 800 c) for a T-GDI engine with a turbocharger, it is still applied to a T-GDI engine because it can cope with the high combustion pressure and pressure wave occurring when pre-ignition occurs. Such a cold type spark plug can cope with pre-ignition, but has problems of ignition failure and deterioration of cold start operation efficiency.

Accordingly, in various embodiments of the present invention, ways to reduce heat dissipation of cold-type spark plugs are disclosed in order to address the above problems of ignition failure and degradation of cold start operating efficiency. The shielding space 350 is located in an intermediate position between the hexagonal nut 400 and the insulator tip 500, and the heat range can be selectively adjusted by the shielding space 350, thereby solving the above problem even if a cold type spark plug is used.

Hereinafter, the shielding space 350 will be explained in detail with reference to fig. 2 to 5. An important factor of the shielding space 350 is a ratio of volume to surface area, and its shape may be variously changed according to design or environment.

Fig. 2 is a view illustrating a structure in which a shielding space 350 is formed between an insulator 200 and a metal case 300 in such a manner that the volume of the shielding space 350 is maximized. A portion of the inner surface 330 of the metal housing 300 is concavely shaped to form a shielded space 350. The shielded space 350 may have a quadrangular cross section. In some embodiments, the shielded space 350 may have a rectangular cross-section defined by a height and a bottom thereof, wherein the dimension of the height is greater than the dimension of the bottom. Accordingly, the overall shape of the shielded space 350 may be a hollow cylinder.

As described above, the inner surface 330 of the metal case 300 facing the insulator 200 is concavely shaped to form an air layer between the insulator 200 and the metal case 300, thereby improving the thermal resistance to about 1000 times that in the conventional art. Therefore, the heat radiation performance of the cold type spark plug is reduced, carbon deposition is prevented, and ignition failure at the cold start of the turbocharger-equipped T-GDI engine is also prevented.

Fig. 3 is a view illustrating a structure in which a shielding space 350 is formed between an insulator 200 and a metal case 300 in such a manner that the volume of the shielding space 350 can be adjusted. A portion of the inner surface 330 of the metal housing 300 is concavely shaped to form a shielded space 350. At this time, the shielding spaces 350 may have an uneven section including concave portions and convex portions alternately arranged on the inner surface 330 at predetermined intervals in the axial direction. Therefore, by changing the number of the concave portions and the convex portions of the shielding spaces 350, the number and the volume ratio of the shielding spaces 350 can be adjusted, so that the spark plug having a heat range suitable for the type of the engine can be applied. The shield space 350 is in the general shape of a hollow cylinder like fig. 2, and further has an uneven side surface including a concave portion and a convex portion. Thus, the ratio of the volume to the surface area of the shielded space 350 may be adjusted.

Fig. 4 is a view illustrating a structure in which a shielding space 350 is formed between an insulator 200 and a metal case 300 in such a manner that the volume of the shielding space 350 can be adjusted in consideration of cost and productivity. A portion of the inner surface 330 of the metal housing 300 is concavely shaped to form a shielded space 350. The shielding space 350 may have a saw-toothed cross section including a threaded portion arranged on the inner surface 330 at a predetermined interval in the axial direction. The effect of the screw part formed on the inner surface 330 of the metal case 300 is the same as the effect of the concave part and the convex part of the shielding space 350 described in fig. 3. Further, since the shape of the threaded portion formed on the inner surface 330 of the metal case 300 is the same as the shape of the threaded portion formed on the outer surface of the metal case 300, manufacturing convenience is improved, manufacturing costs are reduced, and productivity is improved.

Fig. 5 is a view showing a structure in which a shield space 350 is formed between an insulator 200 and a metal case 300 and an adiabatic material 600 is disposed in the shield space 350. A portion of the inner surface 330 of the metal housing 300 is concavely shaped to form a shielded space 350. Accordingly, the insulation material 600 may be disposed in the shielding space 350. The shielded space 350 may have a rectangular cross section like that of fig. 2, but the cross-sectional shape may vary according to design or environment. As shown in fig. 5, in the case where the insulation material 600 is disposed in the shielding space 350, the shielding effect can be maximized. Therefore, even when the spark plug is applied to an engine having an unfavorable ignition condition, such as a T-GDI engine equipped with a low pressure EGR (LP EGR) system and a turbocharger, the cold start operation can be improved, and ignition failure can be prevented.

As is apparent from the above description, in order to solve the following problems in the conventional art: when a cold type spark plug having a shorter length portion for reinforcing an insulator is used, deterioration of cold start operation and failure of ignition occur, various aspects of the present invention provide the following spark plugs: the spark plug can reinforce the insulator by reducing the length of the length portion, and in addition, can adjust the heat radiation performance using the shielding space, thereby selectively adjusting the heat range according to the type of the engine.

As shown in fig. 7, a typical spark plug has such operating characteristics: so that the temperature of the spark plug must quickly reach the self-cleaning temperature at low vehicle speeds and must be below the pre-ignition temperature at high vehicle speeds. In various embodiments of the present invention, by forming a shielding space between an insulator and a metal shell, a spark plug has an operation characteristic represented by a line B in fig. 7, whereby even when a cold type spark plug for enhancing the strength of the insulator is used, heat radiation performance is lowered, ignition stability at initial start-up and in a low load region is improved, and ignition failure is prevented.

Further, since the heat range of the spark plug can be selectively adjusted, a spark plug satisfying the heat range suitable for the type of engine can be used, thereby improving usability. By reducing heat dissipation using a shielding space formed between the insulator and the metal case when initially started, the time taken to reach the self-cleaning temperature is reduced. After the temperature of the spark plug reaches a predetermined temperature, the density in the shielded space decreases, and thus the heat dissipation performance increases, thereby increasing the heat range. Further, since the spark plug having the optimum specification for the type of engine can be manufactured only by changing the metal shell without changing the insulator, the manufacturing cost can be reduced and it is easy to cope with new engine development.

For convenience in explanation and accurate definition in the appended claims, the terms "upper" or "lower", "inner" or "outer", and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing description of specific exemplary embodiments of the invention has been presented for the purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the invention and various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the following claims and their equivalents.

Claims

1. A spark plug, comprising:

a center electrode disposed in a center portion of the spark plug;

an insulator surrounding the center electrode; and

a metal shell surrounding the insulator and having a ground electrode extending downward from a lower end thereof and an inner surface facing the insulator,

wherein the inner surface is concavely shaped to form a shielded space between the concave portion of the inner surface and the insulator for adjusting a thermal range of the spark plug;

wherein the inner surface of the metal shell is concavely shaped to form the shielded space therein; and is

The inner surface has an uneven area including concave portions and convex portions that are alternately formed on the inner surface of the metal shell at predetermined intervals in an axial direction of the spark plug.

2. The spark plug of claim 1, wherein the shielded space is located in an intermediate position between a hex nut surrounding the insulator and an insulator tip of the insulator.

3. The spark plug of claim 1, wherein the inner surface of the metal shell is concavely shaped to form the shielded space in the inner surface, and the shielded space has a quadrilateral cross-section.

4. The spark plug of claim 1, wherein the shielded space has a rectangular cross-section defined by a height and a bottom of the shielded space, the height being greater in size than the bottom.

5. The spark plug of claim 1, wherein:

the inner surface of the metal shell is concavely shaped to form the shielded space therein; and is

An insulating material is disposed in the shielded space.

6. The spark plug of claim 1, wherein the shielded space is generally in the shape of a hollow cylinder.

7. A spark plug, comprising:

a center electrode disposed in a center portion of the spark plug;

an insulator surrounding the center electrode; and

wherein: the inner surface of the metal shell is concavely shaped to form the shielded space therein; and is

The inner surface has a serrated region including threaded portions formed on the inner surface at predetermined intervals in an axial direction of the spark plug.